Search Publications
Solar Type II Radio Bursts and IP Type II Events
Cane, H. V.; Erickson, W. C.
We have examined radio data from the WAVES experiment on the Wind spacecraft in conjunction with ground-based data in order to investigate the relationship between the shocks responsible for metric type II radio bursts and the shocks in front of coronal mass ejections (CMEs). The bow shocks of fast, large CMEs are strong interplanetary (IP) shocks…
Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. III. Measurement for Ursa Minor
Minniti, Dante; Mateo, Mario; Piatek, Slawomir +5 more
This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field contains a quasi-stellar object that serves as the ``reference point.'' The measured proper motion for Ursa Minor, expressed in the equatorial coordinate …
A jet-induced outflow of warm gas in 3C293
Morganti, R.; Tadhunter, C. N.; Holt, J. +3 more
Using long-slit emission-line spectra we detect a fast outflow of ionized gas, with velocities up to 1000 km s-1, in the nearby powerful radio galaxy 3C293 (z= 0.045). The fast outflow is located about 1 kpc east of the nucleus, in a region of enhanced radio emission due to the presence of a distorted radio jet. We present results that …
Radial variations in the Io plasma torus during the Cassini era
Delamere, P. A.; Bagenal, F.; Steffl, A.
A radial scan through the midnight sector of the Io plasma torus was made by the Cassini Ultraviolet Imaging Spectrograph on 14 January 2001, shortly after closest approach to Jupiter. From these data, Steffl et al. (2004a) derived electron temperature, plasma composition (ion mixing ratios), and electron column density as a function of radius fro…
Sensitivity of spectral lines to temperature, velocity, and magnetic field
Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Cabrera Solana, D.
We present an analytical and numerical study of the sensitivity of weak solar photospheric lines to temperature, velocity, and magnetic fields. Our investigation is based on the concept of response functions (Landi degl'Innocenti & Landi degl'Innocenti 1977; Ruiz Cobo & del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetr…
An old quasar in a young dark energy-dominated universe?
Friaça, A. C. S.; Alcaniz, J. S.; Lima, J. A. S.
Dark energy is the invisible fuel that seems to drive the current acceleration of the Universe. Its presence, which is inferred from an impressive convergence of high-quality observational results along with some apparently successful theoretical predictions, is also supported by the current estimates of the age of the Universe from dating of loca…
Solar Convection-Zone Dynamics, 1995-2004
Thompson, M. J.; Howe, R.; Komm, R. +3 more
The nine-year span of medium-degree helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI) allows us to study the evolving zonal flows in the solar convection zone over the rising phase, maximum, and early declining phase of solar cycle 23. Using two independent two-dimensional rotation inversion …
Feeding the Monster: The Nucleus of NGC 1097 at Subarcsecond Scales in the Infrared with the Very Large Telescope
Reunanen, Juha; Prieto, M. Almudena; Maciejewski, Witold
Near-IR images of the prototype LINER/Seyfert type 1 galaxy NGC 1097 observed with the Very Large Telescope using adaptive optics disclose with unprecedented detail a complex central network of filamentary structure spiraling down to the center of the galaxy. The structure, consisting of several spiral arms, some almost completing a revolution abo…
Asphericity and clumpiness in the winds of Luminous Blue Variables
Vink, Jorick S.; Davies, Ben; Oudmaijer, René D.
We present the first systematic spectropolarimetric study of Luminous Blue Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to investigate the geometries of their winds. We find that at least half of our sample show changes in polarization across the strong Hα emission line, indicating that the light from the stars is intrinsical…
Propagation of whistler-mode chorus to low altitudes: divergent ray trajectories and ground accessibility
Santolík, O.; Chum, J.
We investigate the ray trajectories of nonductedly propagating lower-band chorus waves with respect to their initial angle θ0, between the wave vector and ambient magnetic field. Although we consider a wide range of initial angles θ0, in order to be consistent with recent satellite observations, we pay special attention to th…